Rhizobial polysaccharide‐degrading enzymes from roots of legumes

The surface structure and chemistry of symbiotic bacteria from the genus Rhizobium are probably important for the outcome of the infection of legume hosts. Exopolysaccharide, capsular polysaccharide, lipopolysaccharide and a low‐molecular‐weight polysaccharide were isolated from R. trifolii UTC 110‐1 and R. leguminosarum UTC 114‐5 and partially characterized. No or only minor differences in sugar composition could be found for the corresponding fractions from the two organisms. A general method to measure low activities of polymer‐degrading enzymes was developed, and used to determine enzyme activities in root extracts of Trifolium repens L. cv. Lena and Pisum xativiini L. cv. Little Marvel against the isolated rhizobial polysaccharides. An enzyme preparation from T. repens partially degraded all polysaccharides isolated from its symbiont R. trifolii while polysaccharides from R. leguminosarum , symbiont of P. sativum , were degraded to a much lesser extent. Correspondingly, an enzyme preparation from P. sativum degraded all polysaccharides isolated from both its symbiont R. leguminosarum and its non‐symbiont R. trifolii. The amount of symbiont polysaccharides degraded was larger than the amount of polysaccharides degraded from the non‐symbiont R. trifolii.